Process for preparation of anilines substituted by chlorine in the meta-position

ABSTRACT

A process for the dechlorination of aromatic nitro or amino compounds consists in reacting anilines or nitrobenzenes which are polysubstituted by chlorine, with hydrogen, under the action of heat, in the presence of iodide or bromide ions, in the liquid phase and at low pressure. 
     The process makes it possible selectively to obtain anilines which are chlorine-substituted in the meta-position.

FIELD OF THE INVENTION

The present invention relates to a process for the preparation ofanilines substituted by chlorine in the meta-position, by reactinghydrogen with nitrogen-containing aromatic compounds which are morehighly halogen-substituted.

BACKGROUND OF INVENTION

U.S. Pat. No. 4,085,141 describes the preparation of chloroanilinessubstituted in the meta-position, by reacting polychloroanilines withhydrogen. However, the process described in the said patent requires theuse of high pressures and of very large amounts of hydrochloric acid,and this presents serious corrosion problems.

SUMMARY OF THE INVENTION

One object of the invention is to provide a process which makes itpossible to prepare anilines substituted in the meta-position bychlorine, with good yields, from nitrogen-containing aromatic compoundswhich are more highly halogen-substituted.

A further object of the invention is to provide a process for thepreparation of anilines substituted in the meta-position by chlorine, itbeing possible for this process to use either chlorine-substituted nitrocompounds (substituted nitrobenzenes and the like) orchlorine-substituted amino compounds (polychloroanilines and the like)as the starting reactant.

A further object of the invention is to provide a process for thepreparation of anilines substituted in the meta-position by chlorine,using moderate pressures.

A further object of the invention is to provide a process for thepreparation of anilines substituted in the meta-position by chlorine,using moderate reaction temperatures.

Yet another object of the invention is to provide a process for thepreparation of anilines substituted in the meta-position by chlorine,using moderately corrosive conditions.

Further objects and advantages of the invention will become apparent inthe course of the description which now follows.

DETAILED DESCRIPTION OF EMBODIMENTS

It has now been found that these objects can be achieved by virtue of aprocess for the preparation of anilines substituted in the meta-positionby chlorine, which process consists in carrying out the catalytichydrogenation of nitrogen-containing benzene derivatives, in the liquidphase, in an acid medium, under the action of heat, under pressure andin the presence of noble metals from group VIII of the periodicclassification, and in which process the benzene derivatives have theformula: ##STR1## in which: Y represents the hydrogen atom or the oxygenatom, X' and X", which are identical or different from one another, eachrepresent a chlorine atom or an optionally substituted alkyl, aryl,aralkyl, alkoxy or aralkoxy radical, it being furthermore possible forone of the symbols X' and X" to be a hydrogen atom (when preparingmonochloroanilines (meta-chloroanilines), only one of the substituentsX' or X" represents the chlorine atom, and when preparingdichloroanilines (disubstituted by chlorine in the meta-position), bothof the symbols X' and X" represent the chlorine atom), and R', R" andR'", which are identical or different from one another, each represent achlorine atom or an optionally substituted alkyl, aralkyl, alkoxy oraryloxy radical, at least one of these three symbols representing thechlorine atom and it being furthermore possible for at most two of thesymbols R', R" or R"' to be hydrogen, and the reaction is carried out inthe presence of iodide and/or bromide ions.

As already stated, the reaction is carried out in the liquid phase; inpractice, it is advantageously carried out in the presence of aninorganic or organic solvent which is liquid and inert under theoperating conditions. The term inert solvent is understood as meaning asolvent which does not undergo chemical reaction. In fact, the use ofwater is preferred.

The acidity of the reaction medium is generally such that the pH (in thecase of an aqueous medium) is advantageously less than 1.5 andpreferably less than 1. The concentration of H⁺ ions in the medium isgenerally between 0.5 and 12 g.ions/liter and preferably between 1 and 6g.ions/liter.

The highest concentrations of acid can be used but no significantadvantage is gained.

The acidity of the reaction medium can be achieved by means of strongmineral acids, such as sulphuric, phosphoric or hydrogen halide acids,or strong organic acids; however, it is preferred to use hydrogen halideacids and more especially hydrochloric acid. In any case, in view of thepresence of chloride ions originating from the dehalogenation and thepresence of iodide or bromide ions which are characteristic of theinvention, the reaction is in fact always carried out, at least in part,in the presence of hydrochloric, hydriodic and/or hydrobromic acids.However, insofar as these acids are dissociated in the medium, there isno point in defining the acids used and it is preferable to indicate, asabove and below, the acid strength (pH or concentration of H⁺) and alsothe nature and the concentration of anions required for the reaction(halide anions).

The process according to the invention is carried out in the liquidphase (with the exception, of course, of the catalyst based on a noblemetal, which most commonly constitutes a solid phase). The liquid phasecan be homogeneous and constitute a solution; this is a preferredprocedure, in particular in the case where Y is an oxygen atom in theformula (I); a liquid phase of this type therefore contains thereactants, the reaction products and the solvent or solvents which maybe present. It is also possible to carry out the reaction with twoliquid phases.

The pressure at which the reaction is carried out is generally more than3 bars (relative pressure) and preferably more than 5 bars. There is nocritical upper limit for the pressure, but, for economic reasons, it isgenerally advantageous to operate at pressures of less than 100 bars,pressures of less than 30 bars being preferred.

The reaction temperature is generally between 90° and 300° C. andpreferably between 110° and 200° C. In the case where relativelyvolatile acids are used, an elevated temperature can lead to arelatively high partial pressure of the compounds, other than hydrogen,in the vapour phase (the term vapour phase is obviously understood asmeaning the vapour phase above the liquid reaction medium). Theoperating conditions are generally chosen so that the hydrogen partialpressure is between 10 and 80% of the total pressure (relative pressure)and preferably between 30 and 60%.

The noble metals constituting the base of the catalysts used in theinvention are mainly metals from group VIII of the periodicclassification, such as ruthenium, rhodium, palladium, osmium, iridiumand platinum; palladium is the preferred metal. The metal can be in themetallic form or in the form of a chemical compound; in general, themetal is preferably employed in the metallic form because, under theoperating conditions, the compounds tend to be reduced to the metallicform (oxidation state=zero). The catalyst can be supported orunsupported. Any support which is in itself known for supportingcatalysts can be used as the catalyst support, provided that thissupport is resistant to water and acids; activated carbon, silica andbarium sulphate may be mentioned as being more particularly suitable assupports; carbon black is a preferred support. Both the catalyst and itssupport are advantageously in the finely divided form; specific surfaceareas of more than 100 m² /g are generally very suitable.

The amount of catalyst employed is such that the proportion by weight ofnoble metal from the catalyst, relative to the compound of the formula(I) to be treated, is generally between 0.05 and 10% and preferablybetween 0.5 and 5%.

The iodide and/or bromide ions employed in the reaction can beintroduced in the most diverse forms, in particular in the form ofhydriodic and/or hydrobromic acids, but it is generally more convenientto introduce them in the form of halides (iodides and/or bromides) orhydrohalides (hydroiodides and/or hydrobromides). The iodides orbromides are usually alkali metal or alkaline earth metal iodides orbromides, such as the iodides or bromides of lithium, sodium, potassiumor ammonium. These ammonium salts can be quaternary ammonium salts ornon-quaternary ammonium salts (eg. NH₄ ⁺). The hydroiodides orhydrobromides are preferably hydroiodides or hydrobromides of asubstituted aniline such as the amine of the formula (I) (Y=H) and/orthe substituted aniline produced according to the invention. As alreadystated, chloride ions are formed during the reaction with the resultthat, from a formal point of view, it is always possible to considerthat the reaction takes place in the presence of hydrochloric acid. Theamount of iodide ions in the reaction medium is most commonly between10⁻⁶ and 1 g.ion/liter and preferably between 0.0001 and 0.1g.ion/liter. The use of small amounts of iodide ions is especiallyadvantageous in that it is generally unnecessary to recover them at theend of the reaction. The amount of bromide ions in the reaction mediumis most commonly between 0.01 and 10 g.ions/liter and preferably between0.1 and 6 g.ions/liter.

The following may preferably be mentioned as compounds of the formula(I) which can be treated by the process of the invention:2,3-dichloronitrobenzene and 2,3-dichloroaniline,2,5-dichloronitrobenzene and 2,5-dichloroaniline,3,4-dichloronitrobenzene and 3,4-dichloroaniline,2,3,4-trichloronitrobenzene and 2,3,4-trichloroaniline,2,3,5-trichloronitrobenzene and 2,3,5-trichloroaniline,2,3,6-trichloronitrobenzene and 2,3,6-trichloroaniline,2,4,5-trichloronitrobenzene and 2,4,5-trichloroaniline,3,4,5-trichloronitrobenzene and 3,4,5-trichloroaniline,2,3,4,6-tetrachloronitrobenzene and 2,3,4,6-tetrachloroaniline,2,3,4,5-tetrachloronitrobenzene and 2,3,4,5-tetrachloroaniline,2,3,5,6-tetrachloronitrobenzene and 2,3,5,6-tetrachloroaniline, andpentachloronitrobenzene and pentachloroaniline, but also4,5,6-trichloro-2-methylnitrobenzene and4,5,6-trichloro-2-methylaniline, 2,5-dichloro-4-methylnitrobenzene and2,5-dichloro-4-methylaniline, 2,3,5,6-tetrachloro-4-methylnitrobenzeneand 2,3,5,6-tetrachloro-4-methylaniline,2,5-dichloro-3,4-dimethylnitrobenzene and2,5-dichloro-3,4-dimethylaniline, 2,5-dichloro-4-ethylnitrobenzene and2,5-dichloro-4-ethylaniline, 2,5-dichloro-4-propylnitrobenzene and2,5-dichloro-4-propylaniline, 3,4,6-trichloro-2-benzylnitrobenzene and3,4,6-trichloro-2-benzylaniline,2,2'-dinitro-3,5,6,3',5',6'-hexachlorodiphenylmethane and2,2'-diamino-3,5,6,3',5',6'-hexachlorodiphenylmethane,2-nitro-3,4,5-trichlorodiphenyl and 2-amino-3,4,5-trichlorodiphenyl,4,4'-dinitrooctachlorodiphenyl and 4,4'-diaminooctachlorodiphenyl,4,5-dichloro-2-methoxynitrobenzene and 4,5-dichloro-2-methoxyaniline,3,4-dichloro-2-methoxynitrobenzene and 3,4-dichloro-2-methoxyaniline,3,6-dichloro-2-methoxynitrobenzene and 3,6-dichloro-2-methoxyaniline,5,6-dichloro-2-methoxynitrobenzene and 5,6-dichloro-2-methoxyaniline,3,4,6-trichloro-2-methoxynitrobenzene and3,4,6-trichloro-2-methoxyaniline, 3,4,5-trichloro-2-methoxynitrobenzene,and 3,4,5-trichloro-2-methoxyaniline,3,4,5,6-tetrachloro-2-methoxynitrobenzene and3,4,5,6-tetrachloro-2-methoxyaniline, 4,5-dichloro-3-methoxynitrobenzeneand 4,5-dichloro-3-methoxyaniline, 5,6-dichloro-3-methoxynitrobenzeneand 5,6-dichloro-3-methoxyaniline, 2,5-dichloro-3-methoxynitrobenzeneand 2,5-dichloro-3-methoxyaniline, 4,5,6-trichloro-3-methoxynitrobenzeneand 4,5,6-trichloro-3-methoxyaniline,2,4,5,6-tetrachloro-3-methoxynitrobenzene and2,4,5,6-tetrachloro-3-methoxyaniline, 2,3-dichloro-4-methoxynitrobenzeneand 2,3-dichloro-4-methoxyaniline, 2,5-dichloro-4-methoxynitrobenzeneand 2,5-dichloro-4-methoxyaniline, 2,3,6-trichloro-4-methoxynitrobenzeneand 2,3,6-trichloro-4-methoxyaniline,2,3,5-trichloro-4-methoxynitrobenzene and2,3,5-trichloro-4-methoxyaniline,2,3,5,6-tetrachloro-4-methoxynitrobenzene and2,3,5,6-tetrachloro-4-methoxyaniline, 4,5-dichloro-2-phenoxynitrobenzeneand 4,5-dichloro-2-phenoxyaniline,3,4,5,6-tetrachloro-2-phenoxynitrobenzene and3,4,5,6-tetrachloro-2-phenoxyaniline,2,4,5,6-tetrachloro-3-phenoxynitrobenzene and2,4,5,6-tetrachloro-3-phenoxyaniline, 2,5-dichloro-4-phenoxynitrobenzeneand 2,5-dichloro-4-phenoxyaniline, and2,3,5,6-tetrachloro-4-phenoxynitrobenzene and2,3,5,6-tetrachloro-4-phenoxyaniline.

The following may preferably be mentioned amongst the anilines which aresubstituted in the meta-position by a chlorine atom and can be preparedby the process according to the invention: meta-chloroaniline and3,5-dichloroaniline, but also: 5-chloro-2-methylaniline,5-chloro-3-methylaniline, 3-chloro-4-methylaniline,3,5-dichloro-4-methylaniline, 5-chloro-3,4-dimethylaniline,3-chloro-4-ethylaniline, 3-chloro-2-benzylaniline,4,4'-diamino-2,6,2',6'-tetrachlorodiphenyl, 3-chloro-2-methoxyaniline,5-chloro-2-methoxyaniline, 3,5-dichloro-2-methoxyaniline,3-chloro-4-methoxyaniline, 5-chloro-3-methoxyaniline,3,5-dichloro-4-methoxyaniline, 3-chloro-2-phenoxyaniline,5-chloro-2-phenoxyaniline, 3,5-dichloro-2-phenoxyaniline and3,5-dichloro-4-phenoxyaniline.

The process according to the invention can be carried out continuouslyor discontinuously. At the end of the reaction, the catalyst can beseparated off, if necessary, by filtration or by equivalent means suchas draining; the amine prepared, which is chlorine-substituted in themeta-position, can be separated off by any means which is in itselfknown, e.g. by solvent extraction and/or by distillation; beforecarrying out this separation, it is generally appropriate to convert theamine (salified in an acid medium) back into the form of an (unsalified)amine by rendering the reaction mixture neutral or alkaline with the aidof an alkaline agent. In the case of a process which uses bromine ions,it can be advantageous to recover these ions in order to recycle theminto a subsequent operation.

The process according to the invention is very advantageous because ofits good selectivity with respect to the amine which ischlorine-substituted in the meta-position, and because of the relativelymild conditions under which it can be carried out. The amines producedin this way, which are chlorine-substituted in the meta-position, can beused, in particular, for manufacturing pesticides.

The following examples, which are given without implying a limitation,illustrate the invention and show how it can be put into effect.

EXAMPLE 1

2,3,4,5-Tetrachloroaniline (1.67 g), a catalyst consisting of palladiumdeposited on activated carbon (specific surface area of the activatedcarbon: 1,100 m² /g; proportion of palladium by weight: 10%) (0.07 g),an aqueous solution of hydrochloric acid having a concentration of 4mols/liter (106 cc) and an aqueous solution of hydriodic acid having aconcentration of 7.6 mols/liter (13.3 cc) are introduced into a 250 ccautoclave coated on the inside with tantalum.

The autoclave is closed and purged first with argon and then withhydrogen. The temperature is then raised to 190° C., whilst allowing theautogenous pressure to increase, and then, when this temperature hasbeen reached, hydrogen is introduced until the total (relative) pressureis 20 bars, the hydrogen partial pressure being 6 bars.

The reaction is allowed to proceed under these conditions for 1 hour.After cooling, the liquid reaction mixture is rendered alkaline with anaqueous solution of sodium hydroxide (NaOH); the catalyst is filteredoff; the 3,5-dichloroaniline is extracted from the aqueous phase usingmethylene chloride; the methylene chloride solution thus obtained isdried over sodium sulphate; the solvent is evaporated off in vacuo; thedegree of conversion of the tetrachloroaniline was 100% and the yield of3,5-dichloroaniline was 98.2%.

EXAMPLE 2

Example 1 is repeated with the following modifications: an aqueoussolution of hydrochloric acid having a concentration of 0.8 mol/liter(98 cc) (instead of a solution having a concentration of 4 mols/liter(106 cc)) is used and dry NaI (63 g) (instead of a solution of HI (13.3cc)) is used.

3,5-Dichloroaniline is obtained with a yield of 92.2%. The degree ofconversion of the tetrachloroaniline is 100%.

EXAMPLE 3

Example 1 is repeated with the following modifications: an aqueoussolution of hydrochloric acid having a concentration of 0.8 mol/liter(115 cc) (instead of a solution having a concentration of 4 mols/liter(106 cc)) is used and dry NaI (14.8 g) (instead of a solution of HI(13.3 cc)) is used.

3,5-Dichloroaniline containing 5.8% of trichloroaniline and 0.3% ofmeta-chloroaniline is obtained; the yield of dichloroaniline is 93.6%;the degree of conversion of the tetrachloroaniline is 100%.

EXAMPLE 4

Example 1 is repeated with the following modifications: an aqueoussolution of hydrochloric acid (120 cc instead of 106 cc) is used, anaqueous solution of hydriodic acid having a concentration of 0.01mol/liter (0.4 cc) (instead of a solution having a concentration of 7.6mols/liter (13.3 cc)) is used and the reaction lasts 5 hours (instead of1 hour).

3,5-Dichloroaniline containing 3.5% of meta-chloroaniline is obtainedwith a yield of 96% of 3,5-dichloroaniline and a degree of conversion ofthe tetrachloroaniline of 100%.

EXAMPLE 5

Example 1 is repeated with the following modifications:tetrachloroaniline (0.42 g instead of 1.67 g) is introduced, an aqueoussolution of hydrochloric acid having a concentration of 2.5 mols/liter(120 cc) (instead of a solution having a concentration of 4 mols/liter(106 cc)) is introduced, dry KI (0.11 g) (instead of a solution of HI(13.3 cc)) is introduced, the reaction lasts 2 hours 40 minutes (insteadof 1 hour), the temperature is 150° C. (instead of 190° C.) and thepressure is 10 bars, the hydrogen partial pressure being 5 bars.

3,5-Dichloroaniline containing 2.5% of aniline and 2.5% ofmeta-chloroaniline is obtained with a yield of 3,5-dichloroaniline of86%. Degree of conversion of the tetrachloroaniline: 100%.

EXAMPLE 6

Example 1 is repeated with the following modifications:2,3-dichloroaniline (1.17 g) (instead of tetrachloroaniline) is used, apalladium-based catalyst (0.56 g instead of 0.07 g) is used, an aqueoussolution of HCl having a concentration of 2.5 mols/liter (120 cc)(instead of a solution of HCl having a concentration of 4 mols/liter(106 cc)) is used and KI (0.2 g) (instead of hydriodic acid) is added.

The temperature is raised to 160° C.; the total pressure is 13 bars (thehydrogen partial pressure being 6 bars); the reaction time is 3 hours.

The degree of conversion of the 2,3-dichloroaniline is 98.2%; the yieldof meta-chloroaniline is 95.6%, relative to the dichloroanilineconverted.

EXAMPLE 7

Example 6 is repeated with the following modifications:3,4-dichloroaniline (instead of 2,3-dichloroaniline) is used,hydrochloric acid having a concentration of 1 mol/liter (instead of 2.5mols/liter) is used, KI (0.04 g instead of 0.2 g) is used and thereaction time is only 45 minutes.

The 3,4-dichloroaniline is completely converted; meta-chloroaniline isobtained with a yield of 97.1%.

EXAMPLE 8

3,4-Dichloronitrobenzene (139 g), a catalyst (palladium on carbon black,containing 10% of palladium) (0.56 g), an aqueous solution ofhydrochloric acid having a concentration of 1 mol/liter (120 cc) and KI(0.04 g) are introduced into a 225 cc autoclave.

The autoclave is purged with argon and then with hydrogen, and hydrogenis introduced into the autoclave until the pressure is 4 bars. Thetemperature of the autoclave is raised to 160° C. The pressure is then13 bars, the hydrogen partial pressure being 6 bars.

The reaction is allowed to proceed for 1 hour 40 minutes and theautoclave is cooled. The degree of conversion of thedichloronitrobenzene is 100%. Meta-chloroaniline was obtained with ayield of 92.9%.

EXAMPLE 9

A 4 N aqueous solution of hydrochloric acid (120 cc),3,4,5-trichloroaniline (0.354 g), a palladium-based catalyst such asthat used in Example 1 (0.14 g) and KI (0.011 g) are introduced into a250 cc autoclave coated on the inside with tantalum.

The autoclave is closed and purged with argon and then with hydrogen. Itis heated at 130° C. for 2 hours 30 minutes under a total pressure of 8bars and a hydrogen partial pressure of 5 bars. During the reaction, thetrichloroaniline was entirely converted and 3,5-dichloroaniline wasobtained with a yield of 99%.

EXAMPLE 10

A 4 N aqueous solution of HCl (120 cc), 2,4,5-trichloroaniline (3.54 g),a palladium-based catalyst such as that used in the preceding examples(palladium on activated carbon containing 10% of palladium) (1.4 g) andpotassium iodide (0.011 g) are introduced into a 250 cc autoclave coatedon the inside with tantalum.

The autoclave is closed and purged with argon and then with hydrogen. Itis heated at 160° C. for 240 minutes under a total pressure of 18 barsand a hydrogen partial pressure of 13 bars.

The conversion is complete and 3-chloroaniline is obtained with a yieldof 98.2%.

EXAMPLE 11

The procedure of the preceding example is followed, except for thefollowing conditions:

A 4 N aqueous solution of HCl (120 cc), 2,3,5-trichloroaniline (0.354g), a palladium-based catalyst (palladium on carbon activated containing10% of palladium) (0.140 g) and potassium iodide (0.011 g) areintroduced.

The autoclave is heated at 160° C. for 160 minutes under a totalpressure of 18 bars, the hydrogen pressure being 13 bars.

The conversion is complete and 3,5-dichloraniline is obtained with ayield of 96.8%.

EXAMPLE 12

The procedure of Example 1 of the patent is followed, except for thefollowing conditions:

An aqueous solution of hydrochloric acid containing 4 mols/liter (120cc), 2,3,4,5-tetrachloroaniline (1.67 g), the catalyst used in Example 1(0.07 g) and potassium bromide (7.14 g) are introduced.

The autoclave is heated at 190° C. for 170 minutes under a totalpressure of 20 bars, the hydrogen pressure being 6 bars.

The conversion is total. 3,5-Dichloroaniline is obtained with a yield of90%.

EXAMPLE 13

The procedure of Example 1 is followed, except for the followingconditions:

4 N aqueous hydrochloric acid (120 ml), 2,3,4,5-tetrachloroaniline (420mg), the catalyst used in Example 1 (140 mg) and potassium iodide (1.1mg, i.e. a concentration of 5.5.10⁻⁵ in the medium) are introduced.

The autoclave is heated at 160° C. for 220 minutes under a totalpressure of 9 bars, the hydrogen pressure being 4.5 bars.

The conversion of the tetrachloroaniline is complete.3,5-Dichloroaniline is obtained with a yield of 92.5%.

EXAMPLE 14

The procedure of Example 1 is followed, except for the followingconditions:

4 N aqueous hydrochloric acid (120 ml), 2,3,4,5-tetrachloroaniline (420mg), a catalyst containing 1.1% of palladium deposited on activatedcarbon (140 mg) and potassium iodide (11 g) are introduced.

The autoclave is heated at 160° C. for 180 minutes under a totalpressure of 18 bars, the hydrogen pressure being 13 bars.3,5-Dichloroaniline is obtained with a yield of 98.1%. The conversion ofthe tetrachloroaniline is complete.

EXAMPLE 15

The same result as in Example 14 is obtained, using the same startingmaterials and the same conditions, by replacing the catalyst containing1.1% of palladium (140 mg) by a catalyst containing 2.8% of palladiumdeposited on the same support by the same method (140 mg).

EXAMPLE 16

A 13.6% strength aqueous solution of hydrochloric acid (2 kg), acatalyst consisting of palladium deposited on activated carbon (specificsurface area of the carbon black: 1,100 m² /g; proportion of palladiumby weight: 10%) (150 g) and dry solid potassium iodide (11.7 g, i.e. 0.5g.ion of iodide ion per gram atom of palladium) are introduced into a3.6 liter autoclave coated on the inside with tantalum.

The autoclave is closed and purged first with nitrogen and then withhydrogen. Hydrogen is then injected until the pressure is 3 bars. Thetemperature is raised to 160° C., whilst allowing the autogenouspressure to increase. Further hydrogen is injected in order to establisha pressure of 15.5 bars, the hydrogen partial pressure being 10 bars.2,3,4,5-Tetrachloronitrobenzene (1 mol) is then injected in the courseof 2 hours 30 minutes.

The reaction is allowed to proceed under these conditions for 2 hours,whilst stirring. The reactor is cooled to 100° C. and then emptied; theliquid reaction medium is neutralised with aqueous sodium hydroxide; thecatalyst is filtered off and the chlorine-substituted amines, mainly3,5-dichloroaniline, are extracted with toluene. The solvent isevaporated off in vacuo.

Under these conditions, the degree of conversion of the2,3,4,5-tetrachlorobenzene is 100% and the yield of 3,5-dichloroanilineis 94%.

I claim:
 1. A process for the preparation of anilines substituted in themeta-position by chlorine, by the catalytic hydrogenation ofchlorine-substituted nitrogen-containing benzene derivatives, in theliquid phase, in an acid medium, under the action of heat, underpressure and in the presence of noble metals from group VIII of theperiodic classification, in which process the benzene derivatives havethe formula: ##STR2## in which Y represents the hydrogen atom or theoxygen atom, X' and X", which are identical or different from oneanother, each represent a chlorine atom or an optionally substitutedalkyl, aryl, aralkyl, alkoxy or aralkoxy radical or one of X' and X" inhydrogen, and R', R" and R"', which are identical or different from oneanother, each represent a chlorine atom or an optionally substitutedalkyl, aralkyl, alkoxy or aryloxy radical, at least one of these threerepresenting the chlorine atom and at most two of R', R" and R"' beinghydrogen, andthe reaction is carried out in an aqueous medium in whichthe pH is less than 1.5 and/or the concentration of H⁺ ions in theaqueous reaction medium is between 0.5 and 12 g.ions/liter, in thepresence of iodide and/or bromide ions and in which the proportion ofiodide ions in the reaction medium is at least 10⁻⁶ g.ions/liter and/orthe proportion of bromide ions in the reaction medium is at least 0.01g.ion/liter.
 2. A process according to claim 1, in which R', R", R"', X'and X", which are identical or different from one another, represent thehydrogen atom or the chlorine atom.
 3. A process for the preparation ofoptionally substituted meta-dichloranilines, according to one of claims1 or 2, in which X' and X" represent the chlorine atom.
 4. A process forthe preparation of optionally substituted meta-monochloroanilines,according to one of claims 1 or 2, in which only one of the two radicalsX' and X" is the chlorine atom.
 5. A process for the preparation of3,5-dichloroaniline, according to claim 1, in which Y is the hydrogen oroxygen atom, X' and X" are the chlorine atom and R', R" and R"' are thehydrogen atom or the chlorine atom, at least one of them being thechlorine atom.
 6. A process according to claim 1, in which the pH isless than 1 and/or the concentration of H⁺ ions in the reaction mediumis between 1 and 6 g/ions/liter.
 7. A process according to claim 1, inwhich the reaction medium consists only of a liquid phase, except forthe catalyst based on a noble metal.
 8. A process according to claim 1,in which the total pressure is between 3 and 100 bars.
 9. A processaccording to claim 10, in which the total pressure is between 5 and 30bars.
 10. A process according to claim 1, in which the temperature isbetween 90° and 300° C.
 11. A process according to claim 1, in which thehydrogen partial pressure is between 10 and 80% of the total pressure.12. A process according to claim 10, in which the hydrogen partialpressure is between 30 and 60% of the total pressure.
 13. A processaccording to claim 1, in which the noble metal catalyst is palladium.14. A process according to claim 1, in which the proportion by weight ofnoble metal, relative to the compound of the formula (I), is between0.05 and 10%.
 15. A process according to claim 1, in which theproportion of iodide ions in the reaction medium is between 10⁻⁶ and 1g.ion/liter and/or the proportion of bromide ions in the reaction mediumis between 0.01 and 10 g.ions/liter.
 16. A process according to claim14, in which the proportion of iodide ions in the reaction medium isbetween 0.0001 and 0.1 g.ion/liter and/or the proportion of bromide ionsis between 0.1 and 5 g.ion/liter.
 17. A process according to claim 1, inwhich the temperature is between 110° and 200° C.
 18. A processaccording to claim 7, in which the proportion by weight of noble metalcatalyst, relative to the compound of formula (I), is between 0.5 and5%.
 19. A process according to claim 2 or 5, in which the reactionmedium consists only of a liquid phase, except for the catalyst bseed ona noble metal; the total pressure is between 3 and 30 bars; thetemperature is between 90° and 200° C.; the hydrogen partial pressure isbetween 10 and 80% of the total pressure; and the noble metal catalystis palladium present in an amount between 0.05 and 10% relative to thecompound of formula (I).